Eyes on Arctic Sea Ice

The scientific world is watching the daily satellite image updates of the shrinking Arctic Circle sea ice to see if it will set a new record as it heads toward its smallest size of the year at the summer’s end.

“Are we at the minimum?” said Mark Serreze, senior research scientist at the National Snow and Ice Data Center in Boulder, in a telphone interview Tuesday.

“We’ve still got a little ways to go. The earliest it has ever happened is Sept. 3 and the latest is Sept. 22. It could be any day now.”

Kat Wade/The Chronicle

Polar bears greet on Alaska’s Barter Island in the Beaufort Sea in September 2005.

Since NASA started sending satellite images of the floating frozen water 30 years ago, the minimum size of the Arctic pack ice has declined by 10 percent per decade. The scientists say the melt is most likely associated with human-caused global warming, and they debate models that project an ice-free summer anywhere from 2012, to 2050 to the end of the century.

The changes in the pack ice and the glaciers wreak very real changes on Arctic settlements. The people living along the coasts, including American and Canadian Eskimos, see erosion of the coastlines and disruption of fishing and hunting patterns. Polar bears, walruses and ice seals are losing hunting and reproduction territory, and face new threats on land away from their sea-ice home. Nations are beginning to compete over natural resources and the potential for new development opportunity in the newly opening waters

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At the end of August, the size of the Arctic sea ice reached the second lowest on record. The lowest was in August 2007. On Sept. 3, the extent was 1.87 million square miles, 800,000 square miles below the 1979 to 2000 average. This is the fastest rate of daily ice loss that scientists have every observed during a single August.

The ice loss, first in the Beaufort Sea off the coast of Alaska and then shifting to the Chukchi and East Siberian sea, was linked to a shift in atmospheric circulation. Air temperatures in the Chukchi Sea were 9 to 13 degrees higher than normal.

According to scientists from the University of Washington’s Applied Physics Lab Polar Science Center, the sea surface temperatures for August correspond with areas of ice retreat.

When the ice melts, it exposes open water that absorbs solar energy. The warm ocean waters then favor further sea ice melt, they say.

As the temperatures begin to rise, the sea ice reforms, reaching its largest size in the winter.

The sea ice affects the workings of the climate on the whole planet because it regulates exhanges of heat, moisture and salinity in the polar oceans.